Uptake of 14C-L-Glutamic Acid by Daucus carota Cell Suspension in Different Shock Situations

Cell suspension cultures of Daucus carota were shocked by inoculation or by temperature, salts or osmotica in combination with inoculation. Changes in cell vitality were measured by uptake studies with labelled L-glutamic acid performed during the first 30 min after shock treatment. The cell sample was then collected on filter and counted in a liquid scintillation counter. Inoculation alone caused a marked decrease in uptake. Normal uptake capacity was re-established within 2 h. Temperatures of 0?20°C as against 27°C gave an additional decrease in uptake. Of the tested osmotica, polyethylene glycol gave the greatest stabilizing effect on the glutamic acid uptake and sucrose the least. The highest uptake rates were obtained with a calcium concentration of 0.10–0.15 mM.     

Production and oxidation of methane in a boreal mire after a decade of increased temperature and nitrogen and sulfur deposition

Natural wetlands are the single largest source of atmospheric methane (CH₄). Both a changed climate and deposition of anthropogenic nitrogen and sulfur can alter the production and oxidation of CH₄ respectively and thereby also CH₄ exchange. We used a long‐term (12 years) factorial field experiment in a boreal oligotrophic mire to evaluate the effects of greenhouse cover and addition of ammonium nitrate and sodium sulfate on the production and oxidation of CH₄ by applying laboratory incubations of samples from five depths in the mire. The rates of CH₄ production were measured without amendments and after the addition of either glucose or sulfate. Twelve years of increased nitrogen deposition has changed the mire from a Sphagnum‐dominated plant community to one dominated by sedges and dwarf shrubs. The deposition of nitrogen to the field plots caused increased production of CH₄ in incubations without amendments (34%), and also after amendments with glucose (40%) or sulfate (42%). This indicates increased substrate availability (without amendments) but also a greater abundance of methanogens (glucose amendment). The greenhouse cover caused a decrease in CH₄ production in incubations without amendments (34%), after glucose amendment (20%) and after sulfate amendment (31%). These responses indicate decreased substrate availability (without amendment) accompanied by the reduced abundance of methanogens (glucose amendment). The field application of sulfur had no effect on CH₄ production at the depth where maximal CH₄ production occurred. Closer to the mire surface, however, the rate of CH₄ production was significantly reduced by 32–45%. These results suggest that the deposition of sulfate has altered the vertical distribution of methanogens and sulfate‐reducing bacteria. The oxidation of CH₄ was not significantly affected by any of the long‐term field treatments.     

Anomalous facies and ancient faeces in the latest middle Cambrian of Sweden

The middle Cambrian–Furongian transitional interval was a time of significant biotic and environmental changes. Strata of this age in Scania, southern Sweden, contain two interlayered biofacies, a normal one dominated by trilobites and an anomalous one dominated by phosphatocopines (small bivalved arthropods). In places these biofacies are separated by intervals barren of fossils. In a phosphatocopine facies without trilobites in the upper Agnostus pisiformis Zone at Andrarum we recovered scattered fossil aggregates with a homogeneous composition of tightly packed and stacked phosphatocopines. These aggregates are interpreted as coprolites produced by an undetermined predator, possibly the chaetognath-like protoconodont animal or some other soft-bodied metazoan. The so-called barren intervals of Scania are not necessarily barren of fossils, but only trilobites, brachiopods, and other skeletal elements with a calcium-carbonate composition. The phosphatocopine facies with coprolites in the uppermost part of the A. pisiformis Zone correlates with the trilobite mass extinction at the top of the Marjumiid Biomere in Laurentia and immediately prior to the onset of the Steptoean Positive Carbon Isotope Excursion (SPICE), inferring a global shift in the oceanic chemistry that in Scania favoured phosphatocopines over the more common, trilobite-dominated faunas.     

Crosses between frog populations reveal genetic divergence in larval life history at short geographical distance

A number of studies have documented interpopulation divergence in amphibian larval life-history traits across latitudes. Because many frogs are philopatric and have a patchy habitat distribution, genetic divergence could also exist on a much smaller geographical scale, revealed by recent estimates of population divergence using molecular markers. Whether this divergence is reflected in phenotypic traits is virtually unknown. Using artificial fertilization, individuals of the common frog, Rana temporaria , were crossed from two populations situated 130 km apart and differing in population size. The pattern of size at metamorphosis showed evidence of non-additive effects, as demonstrated by a significant interaction between male and female population of origin. Outbreeding resulted in an increase in metamorph size when eggs from the small population were fertilized with sperm from the large population. In the reciprocal cross, however, the pattern was in the opposite direction, with no significant effect of male population of origin. Genetic divergence of populations separated by a relatively short geographical distance may be more common in frogs than previously acknowledged, with potential implications for conservation of declining amphibian species.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 89 , 189–195.     

Protoplast Cultures from Cell Suspensions of Daucus carota

Protoplasts, enzymatically isolated from cell suspension cultures of Daucus carota, have been grown in small Petri-dishes. After enzyme treatment and washing the protoplasts were plated in agar media. Growth and divisions were viewed through the bottom of the Petri-dishes with a light microscope. Different osmotic stabilizers were tested with respect to their ability to promote wall formation and growth of the protoplasts. Combinations of sucrose, sorbitol and “Modopeg” gave the best results. Electron micrographs of cultured protoplasts revealed normal as well as abnormal nuclear conditions.     

A Revised Medium for Growth of Pea Mesophyll Protoplasts

The nutrient requirements of mesophyll protoplasts from Pisum sativum L. cv. Timo have been investigated and a synthetic and completely defined medium has been designed. A high calcium concentration (12 mM) stimulated both protoplast survival and cell division. The content of iron and zinc was also critical. Additions of nicotinic acid, pyridoxine and thiamine were necessary. The protoplast growth was enhanced when some amino acids were included in the medium. An absolute requirement for auxin and cytokinin was shown. In the revised medium about 90% of the isolated protoplasts survived and formed a cell wall. The first divisions were observed after 5 days and after 1 week 10–20% of the cells had divided at least once.     

Agglutinating Effects of Concanavalin A on Isolated Protoplasts of Daucus carota

The agglutinating effects of Concanavalin A (Con A) on protoplasts isolated from cell suspensions of Daucus carota were studied. Con A was shown to agglutinate the plant protoplasts in a manner similar to the way some animal cells are agglutinated. The agglutination process is dependent on the Concanavalin A concentration, protoplast density, treatment time, the temperature, and the membrane condition, α-D-Methylgluco-pyranosid completely inhibited Con A induced agglutination. The results are discussed in relation to membrane structure and morphology.